Manufacture of rubber goods



Patented Oct. 10, 1933' 1,929,603

* 'UNITED srATss PATENT OFFICE MANUFACTURE OF RUBBER GOODS v Edward Arthur Murphy, Erdington, Birmingham, and Eric William Bower Owen, Walmley, England, assignors to Dunlop Rubber Company Limited, a British corporation No Drawing. Application June 8, 1931, Serial No. 543,015, and in England July 29, 1930 p 7 Claims. (01. 18-58) This invention comprises improvements in or capable of gelling on the application of heat, and relating to the manufacture of goods of rubberthen into a froth of latex mixing which does not or similar material of the kindshereinafter specgel on the application of heat. The former is ified, and is particularly concerned with the then withdrawn from the mixing and is intermanufacture of rubber or similar material of nally heated. The froth of latex mixing capable 0 sponge-like or cellular structure from aqueous of gelling on the application of heat is thus emulsions or dispersions thereof. coagulated. Coagulation proceeds from the sur- In the manufacture of goods of rubber or simface in contact with the hot surface of the formilar material of sponge-like or'cellular structure er or mould proceeding through the deposit to 10 from aqueous emulsions or dispersions prior to the inner surface of the applied layer of non- 65' the present invention the emulsions or disperheat sensitive latex mixing. This'outer nonsions were converted into frothy condition coagulate'd layer is then washed as for instance wherein the froth comprised a gas and the emulwith water or dilute alkali solution. In this mansions or dispersions were still in the reversible ner no outer skin is formed on the coagulated condition and thereafter the frothy mass was .froth of heat sensitive latex mixing.

caused to set to a permanent structure of irre- According to another embodiment of the inversible solid material. vention the surface of the frothy mass of the In processes prior to our present invention, the aqueous emulsions or dispersions aforesaid is outer surface layers of the frothy mass which subjected to the action of a coagulating medium are allowed to come into contact with the setwhich is also capable of swelling the rubber, ting medium generally consists of a thin conthereby rapidly swelling and thus weakening the tinuous skin of rubber which hides the sponge membranes forming the surface walls of the air structure of the material underneath. cells to suchan extent that the cells at the outer The object of the present invention is to manusurface of the deposit are ruptured with escape 25 facture goods of rubber or similar material of of entrained air.

sponge-like or cellular structure from aqueous In this manner an outer surface is obtained emulsions or dispersions thereof wherein the forconsisting substantially of ruptured walls instead mation of the aforesaid continuous surface skins of a more or less continuous skin. For instance, is avoided, thereby permitting the cellular struc a former or mould is dipped into a froth or latex 3O ture of the rubber to be visible. mixing and the deposit obtained on withdrawal 7 According to one embodiment of the invention is immersed in a coagulating and swelling soluthe frothy mass of aqueous emulsions or dispertion such as is described and claimed in Patent 1 sions aforesaid comprising a gas and the emul- No. 1,886,351, November 1, 1932. For example a sions or dispersions still in the reversible condisolution containing acetic acid or an aluminum tion is allowed to set with the exception of the salt as a coagulating agent and benzene and alv outer layer or layers, such layer or layers for cohol as a swelling agent may be used. The instance not being allowed to come into direct membranes forming the surface walls of the air contact with the setting medium. For instance, cells become rapidly swollen and in this manner a former or mould is first dipped into a suitable an outer surface is obtained consisting substan- 40 coagulant solution and is then dipped into a tially of ruptured cells. froth of latex mixing. The deposit thus obtained The emulsions or dispersions comprise by way on withdrawal is allowed to stand for a short of example those consisting of or containing rubperiod, for instance, 20-60 seconds, during which ber, guttapercha, balata or similar vegetable time coagulation takes place commencing from resins, occurring naturally or artificially obtained- 15 the surface in contact with the coagulant and and in vulcanised or unvulcanised condition. proceeding through the deposit to the outer sur- Aqueous dispersions of coagulated rubber, vulface. Before this progressive coagulation reaches canised rubber, synthetic rubber, waste or rethe outer surface the deposit is washed as for claim, may also be employed, if desired, as alterinstance with water or dilute alkali solution. In natives or admixtures. All such materials are 50 this manner the latex which would normally hereinafter generically termed rubber material. form the outer skin is removed. Any of the aforesaid dispersions may contain Another way of carrying out the embodiment the usual known compounding ingredients. of the invention is as follows. For instance, a Concentrates such as are described and claimed former or mould capable of being integrally heatin Patent No. 1,846,164 of February 23, 1932, to

5 ed is first dipped into a froth of latex mixing which may be added any one or more of the usual 1.105-

cold after a definite and controllable time in" terval.

Having now particularly described and asc'ertrained the nature of our said invention and in what manner the same is to be performed, we-d'eclare that what we claim is':

1. A process for the manufacture of goods' of rubber material of sponge-like orcellular structure from aqueous emulsions or dispersions thereof which comprises setting the interior-of a mass of a foamed aqueous dispersion of rubber material while still in the reversible condition and in terrupting the setting of a surface oisaid mass.

2. A process of the type describedwhich comprises dipping' a former into a froth of latex mixing capable of gelling on the, application of heat,

then into a-froth of latex mixing which does not gell 'on the application of heat and on withdrawal of the former heating it and subsequently washing off the outer non-coagulatedlayer.

3. A process as claimed in claim 1 wherein a former or mould is dipped into a froth of latex mixing and the deposit obtained on Withdrawal is immersed in a coagulating and swelling solution comprising an acid and a rubber solvent.

4. A process as claimed in claim 1 wherein a former or mould is dipped in a suitable coagulant solution and then dipped in a froth of latex mixing and withdrawn and allowed to stand for a short period and washing the adhering froth with a dilute alkalin solution before coagulation reaches the outer surface of the deposit of froth.

5'. A process forthe manufacture of goods of rubber material of sponge-like or cellular structure from aqueous emulsions or dispersions thereof which comprises setting a mass of foamed aqueous dispersion of rubber material while still in the reversible condition by penetrating said mass with a setting medium, preventing the settingof an outer surfacerof said mass by said setting medium. 7

6'. A process for the manufacture of goods of rubber material of sponge-like or cellular structure from aqueous emulsions or dispersions there- 'of which comprises dipping a former or mold into a suitable coagulant solutionithereafter dipping said mold into a froth of latex mixing -withdraw ing said mold and washing the outer surfaceof the resulting deposit before coagulation has reached said surface. r r

7.=A' process for the manufacture :of goods, of=-1( 0 rubbermaterial of sponge-like or cellular structure which comprises setting a massof foamed aqueous dispersion of rubber'material and while said mass is still ill-IBVElSlblG condition subiecting the surfacethereoi to -Va coagulating medium 5 7 also containing an a ntto swell the rubber. l

- EDWARD ARTHUR MURPHY. i

ERIC WILLIAM BOWER OWEN.

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